The KISS MAV Explained
The workings of the KISS MAV are surprisingly simple. From the supply tank, oxygen is first buffered by the 1st stage regulator mounted on the valve. Most 1st stage regulator’s normal internal pressure (IP) are set at the factory between 125 psi/8.5 bar and 145 psi/9.9 bar. KISS installs a blanking plug in that first stage so that the IP stays fixed at around 145 psi/9.9 bar, regardless of diver depth. Even when subjected to increased ambient pressure changes at depth, the regulator’s IP remains unchanged, ensuring a constant supply pressure to the outgoing supply line.
The oxygen from the regulator is then buffered again by a tiny 0.0035 size orifice housed inside the MAV, reducing the flow to a fixed rate between .5 and .6 liters a minute. On its own, this constant flow of oxygen entering the loop will generally fall just below the diver's own metabolic consumption rate for oxygen.
In order to add additional gas to increase the oxygen level within the loop, the diver simply depresses the side button on the MAV. The action bypasses the orifice to allow a larger dosage of oxygen to enter the loop. Once the button is let go, the valve, which is mechanically spring loaded, slides shut, returning the oxygen feed back to original fixed flow rate of .5 and .6 liters.
The frequency with which a diver will need to push the button is related to changes in depth and/or workload. Generally, there will be more need for adjustments in shallower depths, and fewer the deeper the diver goes. Experienced KISS diver’s find that during an average dive, they only need to push the gas addition button a few times.
The KISS Manual Add Valve (MAV) is small enough to fit the inside of your palm. It is easy to operate and can be positioned anywhere on the diver’s chest or hip to make access and manipulation easy. As a diver gains familiarity with the unit, the motion to add oxygen when needed will evolve into a quick, almost reflexive motion. This is as simple as it gets for manually maintaining a life-supporting level of oxygen in the loop.
Flow rates can be fine-tuned anywhere between .4 and 1 lpm to fit a diver’s individual metabolic rate by adjusting the 1st stage regulator IP from as low as 117 psi/8 bar to as high as 191 psi/13bar.
The small orifice on the mass flow valve introduces fresh oxygen at a constant, low rate of flow that closely matches the diver's own metabolic rate, eliminating the large spikes in PPO2 that are more likely to occur with ongoing manual addition rebreather at constant, but low rate of flow.